Methods for Determining the Molecular Weight and Solution Properties of Polyurethane Block Polymers

摘要

Molecular weight measurements of polyurethane block copolymers have been made using a GPC multi-detector method and compared to values obtained by the conventional polystyrene standard method and a broad molecular weight distribution calibration standard technique. The multi-detector method proposed in this paper produces more accurate molecular weight values and thus its use should allow for better understanding of molecular weight effects on the structure-property relationships of polyurethane block copolymers. The multi-detector technique can also be used to obtain Mark-Houwink constants and the distribution of average segmental composition with molecular with molecular weight. Mark-Houwink parameters method appear to be more accurate than values calculated using an approach based on broad molecular weight distribution calibration standards and suggest that for a series of polyether polyurethanes in THF, the solvent power decreases with increasing hard segment content. A comparison of the molecular weight values obtained using the various methods indicates that the relative M sub W values normally reported based on a polystyrene calibration can be considered as an upper bound on the absolute M sub W value.